1. Field of the Invention
The present invention relates to an apparatus and a method for tracking a face of a person in an image.
2. Description of the Related Art
Recently, technologies for detecting and tracking a person from a still image or a dynamic picture image (hereinafter referred to as a “person tracking process”) have been attracting attention. Usually a face of a person is used as a detecting and tracking target. This is because the face has both features common with everyone and features different in each person. That is, when the target is set as the face, the face can be detected with the features common with everyone, and an individual can be identified with the features different in each person.
The conventional person tracking process is usually performed as follows. First, the faces of the human are detected from the image to identify face regions using the features common with everyone. Then, a tracking target is selected from the detected faces. Sometimes the selection is automatically performed by performing an individual identification process for each face, and sometimes the selection is performed by visual observation of the human. When the tracking target is selected, face detection is performed in a neighbor (hereinafter referred to as a “next detection region”) of a position where the face is detected in the previous process. Then, the individual identification process is performed for the detected face to realize the tracking. There is also proposed a technology in which, even in the case of failure of the identification process, the position of the person is estimated to continue the tracking based on a recognition result of a speech direction recognition or skin color recognition (see, Japanese Patent Application Laid-Open No. 2004-283959).
In order to enhance robustness and to speed-up the process, there is proposed a technology in which the tracking of the person is realized by setting the clothes color of the person at the tracking target. A technology in which tracking is performed by setting the color whose area becomes the maximum in the subject in a distance measuring frame at the clothes color is proposed as a specific example (see, Japanese Patent Application Laid-Open No. 06-22195). Generally, because the clothes color is frequently kept constant independently of a direction of the face, robustness can be enhanced by tracking the clothes color. The process becomes easy by setting the color at the tracking target, so that the process can be sped-up.